The growing use of cordless devices such portable electronic devices and power tools as well as the increasing need for high capacity energy storage for uses such as electrical vehicles has driven significant research into low-cost, high efficiency, high energy density energy storage devices such as batteries and capacitors (including supercapacitors). Graphene is a promising material for use in such devices, but many graphene-containing devices lack the necessary properties for practical use.
US patent application publication 2011/0080689 discloses ionic liquids for use in ultracapacitors and graphene-based ultracapacitors. ACS Nano 2010, 4, 1227 discloses the exfoliation of graphite oxide in propylene carbonate and thermal reduction of the resulting graphene oxide. ACS Nano 2011, 5, 436 discloses high-performance supercapacitors based on poly(ionic liquid)-modified graphene electrodes. Adv. Mater. 2011, 23, 2833 discloses graphene films used in high-performance supercapacitors. Nano Lett. 2010, 10, 4863 discloses graphene-based supercapacitors with an ultrahigh energy density.